TM 1-1520-238-T-6910597.SYSTEM DESCRIPTION (cont)97(16) Audio Warning System. The audio warning system (fig. 995)provides auditory signals to alert thepilot and CPG of hazardous engine, main rotor speed or stabilator conditions.(a) ENG WARN circuit breaker (CB52), located on the pilot center circuit breaker panel, supplies28 VDC emergency dc bus power to the engine out warning unit.(b) The engine out warning unit monitors both engine power turbine speeds (NP), engine gas turbinespeeds (NG), the power lever position of both engines, and torque developed by each engine. NP sensing isdisabled when the respective engine torque is above 100 foot-pounds. Np sensing is also disabled when therespective PWR lever is not in the FLY position. With the PWR lever in the FLY position, if Np decreases to 92%and torque is below 100 20 foot-pounds, the respective engine out sensor develops a signal to turn on therespective ENGINE OUT indicator on the pilot and CPG master/caution warning panels and triggers the engineout warning unit. The engine out warning unit generates a 700-1700 Hz sweep tone to the pilot and CPGheadsets. If the PWRlevers are moved from theFLY position, Np sensing is disabled. However, when NGdecreases to 63%, the engine out warning is triggered. The engine out warning tone can be reset by pressingeither the ENGINE 1 OUT or ENGINE 2 OUT indicator on the master caution/warning panel.(c) If the speed of the main rotor (NR) decreases to 92% (266 rpm), the engine out warning unitdevelops a signal to turn on the LOW RPM ROTOR indicator on the pilot and CPG master/caution warning paneland triggers a 700-1700 Hz sweep tone to the pilot and CPG headsets. If the rotor rpm increases to 104% (301rpm), the HIGH ROTOR indicator turns on, but an audio tone is not generated. The low rotor speed warning tonecan be reset by pressing either the ENGINE 1 OUT or ENGINE 2 OUT indicator on the master caution/warningpanel.(d) If the stabilator automatic control system fails, the stabilator triggers the engine out warning unit. Theengine out warning unit outputs a 1000 Hz continuous tone to the pilot and CPG headsets. The stabilator tone isreset by the stabilator RESET button on the respective collective stick.